The present disclosure relates to optical films and manufacturing methods therefor, antiglare films, optical layer-attached polarizers, and display apparatuses. In particular, it relates to an optical film for use in a display apparatus (display) such as a liquid crystal display apparatus.
In displays such as liquid crystal display apparatuses, the antiglare property can be exhibited and glares caused by surface reflection can be reduced by providing antiglare films at the display surface side to diffuse light emitted from inside (backlight) or light from outside. Typical antiglare films used heretofore have surface asperities that impart antiglare property to the films.
As shown in FIG. 16, a typical antiglare film 101 is formed by applying a coating material containing microparticles 113 such as irregularly shaped silica microparticles or organic microparticles on a base member 111 and drying the applied coating material. According to an antiglare film having such a structure, the microparticles 113 protruding from an antiglare layer 112 scatter the light incident on the antiglare layer 112 and reduce glares caused by surface reflection.
Investigations have been conducted on the asperity shape that can effectively render the antiglare property to antiglare films. For example, Japanese Patent No. 3821956 suggests selecting a centerline mean roughness and a mean profile peak-valley spacing of the asperity profile from the range of 0.08 to 0.5 μm and the range of 20 to 80 μm, respectively, to prevent glaring. 
To achieve good antiglare property, Japanese Patent No. 3374299 teaches providing a rough asperity and a fine asperity in the surface, in which the centerline mean roughness Ra and the mean spacing Sm of the surface with these asperities are respectively adjusted to 0.1 to 1.0 μm and 20 to 120 μm, the centerline mean roughness Ra and the mean spacing Sm of the rough asperity are respectively adjusted to 0.5 to 1.5 μm and 100 to 300 μm, and the centerline mean roughness Ra and the mean spacing Sm of the fine asperity are respectively adjusted to 0.05 to 0.5 μm and 20 to 70 μm.
Japanese Patent No. 4001320 suggests adjustment of the difference in refractive index between a light-transmitting resin and light-transmitting microparticles constituting an antiglare layer to 0.02 or more and 0.2 or less to improve the transmission clarity without reducing scattering or antiglare property and to maintain a high level of transmission clarity by increasing the haze value and thereby decreasing the glaring at the surface.
The above-described suggestions made in Japanese Patent Nos. 3821956 and 3374299 aim to scatter light in a wide angle range. The surface asperities have minutes periods and the surface profiles have steep angle components. As a result, the screen of the display apparatus appears grayish brown as a whole. In other words, the contrast is degraded.
The suggestion made in Japanese Patent No. 4001320 aims to prevent scintillation by controlling the difference in refractive index between a light-transmitting resin and light-transmitting microparticles, the particle diameter, and the amount of microparticles to be added, thereby increasing the internal scattering. Although a relatively high transmission clarity can be obtained by this arrangement, backscattering caused by internal haze increases and the total luminous transmittance is degraded.
A conceivable approach to solving these problems is to decrease the difference in refractive index between the resin and the particles and to decrease the internal haze. However, it is still difficult to achieve sufficient antiglare property.
In some cases, face plates for providing mechanical, thermal, and weathering protections and improving design are installed in front of (at the viewer's side of) display apparatuses such as liquid crystal displays and organic EL displays. In  such cases, when a rear surface (display apparatus side) of a front plate is flat and happens to come close to the display apparatus such as when the front plate is deflected, Newton's rings occur, which is not desirable.
The problems of deflection of components and resulting occurrence of Newton's rings are particularly severe in the cases where a rear surface component is installed at the rear surface side of a display apparatus. This is because the space between the display apparatus and the component at the rear side is narrowed as the thickness of the display apparatus is reduced and because the size of the display apparatus is increasing. Take a liquid crystal display for example. In a liquid crystal display, a diffusing plate for making illuminance of light from light source uniform in an in-plane direction, a lens film for controlling the viewing angle, and a polarization separation reflection film configured to polarize and separate light for reuse are provided as the rear surface components. However, a polarizing plate at the rear surface side of the liquid crystal panel and disposed in front of these rear surface components usually has a flat surface profile. Thus, occurrence of Newton's rings has been problem for thin liquid crystal displays. In view of the above, an optical film that can suppress occurrence of such Newton's ring has been desired.
It is desirable to provide an optical film and a manufacturing method therefor, an antiglare film, an optical layer-attached polarizer, and a display apparatus that can achieve both good contrast and antiglare property.
It is also desirable to provide an optical film and a manufacturing method therefor, an antiglare film, an optical layer-attached polarizer, and a display apparatus that can achieve both good contrast and antiglare property and that can suppress occurrence of Newton's rings.